Patent GB-791968-A (GB)
Title: Improvements in or relating to process for producing glutamic acid
Inventor: PURVIS JOSEPH L
Filed: 1955-08-29
Abstract: Glutamic acid is recovered from a crude aqueous solution consisting of protein hydrolysates, sugar beet waste liquors or the hydrolysates of sugar beet waste liquors, said solution containing glutamic acid and/or glutamic acid precursor compounds, which process comprises adding a water-soluble inorganic barium compound to said crude aqueous solution, separating a solid phase therefrom at a pH greater than 7 and a dissolved solids content of at least 25 per cent by weight, said solid phase comprising organic impurities in combination with barium and recovering glutamic acid from the treate,d solution in the absence of said impurities.  The adjustment of pH and solids content of the solution may take place before or after addition of the barium compound provided that these conditions obtain at the time of separation of the precipitated organic contaminants.  The precipitate may be separated by any convenient means such as filtration or centrifuging.  Suitable water-soluble barium compounds are barium chloride and barium hydroxide.  Barium carbonate may also be used while the crude aqueous solution is acidic, the pH then being adjusted to a value greater than 7 by addition of alkali, such as sodium hydroxide.  A suitable starting material is Steffen's filtrate having a pH between 9 and 11 and a solids content of at least 40 per cent by weight.  Also suitable is Steffen's filtrate hydrolysate obtained by hydrolysing Steffen's filtrate in conventional manner with acid or alkali.  A preferred embodiment of the invention comprises hydrolysing Steffen's filtrate using barium hydroxide.  The precipitate comprising barium salts of contaminating organic materials may be removed by filtration.  Alternatively, the hydrolysate may be treated with gaseous carbon dioxide to adjust the pH to 9.0 whereby the excess barium ions are precipitated as barium carbonate together with the barium salts of contaminating organic impurities and may be removed by filtration.  It is essential in this embodiment that if the barium carbonate filter cake is washed, the wash water should not be added to the filtrate but should be recycled to be treated again with the water-soluble barium compound.  As other starting materials, there may be used wheat gluten or corn gluten hydrolysed with acid, e.g. hydrochloric or sulphuric acid.  The pH is adjusted to 5 to 7 with sodium hydroxide or ammonia, humin is separated by filtration, the filtrate is concentrated to a solids content of greater than 25 per cent by evaporation, insoluble material is separated and after adjusting the pH to a value above 7, a water-soluble barium compound is added, the barium precipitate is separated by filtration and glutamic acid is recovered from the filtrate.  In examples: (1) concentrated Steffen's filtrate is hydrolysed by heating with aqueous sodium hydroxide, the pH is adjusted to 9.0 by addition of hydrochloric acid, barium chloride solution is added and the resulting precipitate is removed by filtration, sodium carbonate is added to precipitate excess barium ions and after filtration and washing, the filtrate is acidified, concentrated and allowed to stand, whereby glutamic acid crystallizes out; (3) corn gluten is hydrolysed by refluxing with aqueous hydrochloric acid, aqueous sodium hydroxide is added to precipitate humin and after filtration, washing, concentration and removal of inorganic compounds as described above, aqueous barium chloride is added and the resulting precipitate of barium compounds is filtered off, excess barium ions are removed by adding sodium carbonate and filtration and glutamic acid is recovered by acidification and crystallization in conventional manner; (5) concentrated Steffen's filtrate is hydrolysed by heating with aqueous barium hydroxide, the hydrolysate is treated with gaseous carbon dioxide, as described above, and after filtration of the barium compounds precipitated, glutamic acid is recovered from the filtrate in conventional manner. Examples (2) and (4) are comparative examples following the procedures of (1) and (3) respectively, but omitting the removal of contaminating organic impurities as barium salts.